Incandescent-lamp filament and method of making the same.



' To all whom it may concern.-

I I) N I ITED STATES PATENT: OFFICE.

JEAN MIO -HE L oA-NELLo, OF PARIS, FRANCE. INCANDESCENT-LAMP FILAMENT AND METHOD OF MAKING THE S AMl-L Be it known that I, JEAN MICHEL OANELLO, a subject of the King of Greece, and a resident of Paris, France, have invented a new and useful Improvement in Incandescent- Lamp Filaments and Method of Makin the Same, which improvement is fully set' orth in the following specification. v

--The presentinvention relates to incandescent electric lamps, and more (particularly to vacuum lamp filaments an methods of making the same, the said filaments consisting of a conducting metal, such as ruthenium 'or osmium, capable of conducting the current when "cold and havin a higher resistance when heated, associate with oxid of the rare earths which become conductors when heated and give brilliancy'to thefilament.

' the. filament maximum surface with The object of the invention is to provide an incandescent lamp in which a high degree of temperature can be attained, to secure mum section, and toenable the conductivity of the filament to remain the same for the normal running of the lamp.

One meth'd of manufacturing a lampin accordance with this invention is as follows:

(a) The fiZament.Threads of cotton or other porous material which have previously been freed from all foreign substances are impre nated with a solution of rare earthy salts suc as soluble salts of thorium, zirconium,

orcerium-and thenallowed todry. The' threads so obtained are'wound uponsmall give a voluminous base.

- formers similar asto form to those hitherto employed in the manufacture of carbon figfaments. hTdliey arebtlhen calcined by means 0 an oxy y 0 en- 0 1 giving an'exceedingly .hot ame'. 'l liisoperation demands great care in order to obtain perfectly regular filaments throughout their whole length, more especially if the threads are impregnatedwith salts which, when calcined,

During the calciare exclusively composed ofthe oxide of the salts employed. The filaments are then cut to the desired len th and placed in tubes of suitable form. T e are then dipped in'a solution of a salt 0 ruthenium or osmium,v

(preferably the peroxid.') A current ofsulfureted hydrogen is then caused topass in such a manner as to convert the peroxid, which is volatile, into sulfid; It isthen allowe d to dry atlabout' 80 centigradet where'- Martian...

I specifieation of Letters Patent. Application filed August 30,1904. Serial No. 222,778.

Patented Aug. 28, 1906.

u on the filaments are withdrawn. Instead o acting in this manner,-by soaking the fila 'mentsi'n a solution of a salt of ruthenium or of osmium and by the subsequent action ofa current of sulfureted hydro en a current of hydrogen may be supplied W 'ch carries with it vapors of ruthenium or of osmium, while also causing the action of a suitable hydro carbon, such as formic aldehyde, which re- In this operation duces the metallic va ors.

the tube is first of al carefully cleansed and.

lowed to take place.

(1)) Finishing the filament..Af ter the treat-.

ment which has just been described the filai ments are not uniform either as regards their structure-or as regards their electric conductivity, which is variable. The also present a resistance of several thousan of ohms. will therefore be understood that 1t is necessary to render them uniform and to reduce The filaments are seized their resistance. between insulated pincers, which, although traversed by a current, may be mani ulated by the operator without anger. he current of. several hundreds of volts is supplied by any convenient source of electricity, and by means-of resistances or of reduction ele-' ments the volt e may be varied at will.

The filament, hel by the pincers, is immersed in an atmosphere deprived of oxygen and of harmful gases, such as are capable of yielding oxygen by chemical reaction. A stream of reducing-gas, preferably of hydrogen, carrying with it vapors of ruthenium or of-os-' .mium, is then-caused to act with vapors of formic aldehyde or other hydrocarbon, and the electric circuit is then closed progressively upon the filament. The arts of the filament which are either of sma l cross-section or of smaller conductivity than' the oth ers become more heated, and the increase of temperature decomposes the metallic vapors and causes a deposit of metal to take, p ace upon these parts of the filament. The voltage; is progressively diminished until the fila ment is uniform inall parts. Finally the voltage is increased,- thereby raising the temno of forming fusible alloys. ,The terminals are prepared in the ordinary manner and are similar to the terminalsof carbon-lamps. The solution having been placed upon the connections, the salts are reduced by means of I 5 a reducing-gas, increasing the temperature.

((1) Deposit of oxide upon the filament.- The last operation consists in effecting upon the whole surfaceof the filament adeposit of oxids which is absolute] regular and uniform.

This deposit may be e eoted in two different wa s:

irst. The filament, being attached to the terminal and connected to the electric circult provided with resistance, is immersed in an 2 5 atmosphere deprived of oxygen and of harmful gases. Through a tube a neutral gas such as nitrogen, hydrogen, or the like-is supplied, which carries with it vapors of a volatile composition-for example, a thorium compound of acetylacetone ((3 11102); Th.-

This compound is dp aced in the ath of the gaseous current an is heated to vo atilization. The vapors produced are carried along by the gases and in contact with the filament, which 1s maintained at a red heat, they become deposited upon it. At the same time a deposit of carbon is produced (arising fromthe carbon contained in the acetylacetone) which may be caused to disappear by the following treatment: The filament is heated in thoroughly-dry carbonic-acid gas. This carb onicacid gas converts the carbon into carbon monoxid, which escapes and only thorium oxid remains.

thorium 01 the like diluted with water, and the filament being taken as negative pole, with a carbon encil as positive pole, the circuit- (regulated by a resistance the value of which is diminished 'in proportion as the depositof thorium oxid upon the filament increases) is closed. When the deposit is of sufficient thickness, the filament-is dried and heated in vacuo. I

It has been explained above that the first -method forthe-deposit of oxids upon the filament necessitates the employment of acet lacetone of thorium. It IS indispensable or the sake of completeness to give the method a of its preparation, which constitutes, however, no part of my invention present.

The precipitate of hydrates. arising from the precipitation by ammonia or from the solution of oxalates in oxalate of, ammonia is Second. A bath is prepared of nitrate ofdissolved in nitric acid. The nitrates formed are evaporated by a dry process, so as to eliminate the excess of acid. The nitrates are dissolved in a small quantity of water, and to the liquor is added a freshly-prepared solution of acetylacetona'te of sodium. In these conditions the nitrate of thorium gives a precipitate of acetylacetonate of thorium,

o'H(oooH:):

cmooone.

well to first of all expel all t e air contained in this latter by introducing a gas-hydrogen, for examplewhich, even at a high temperature, has no action upon the filament. A vacuum is then formed within the bulb to the greatest possible extent to remove the large quantity of gas which is shut up in the filament.

In certain cases it is advisable to inclose in the bulb a certain quantity of red phosphorus, serving to absorb the gases which may be liberated by the filament when the lamp is running. After the degree of vacuum has been tested the lam is sealed. Finally,

it should be mentione that the portion of metal deposited upon the oxids should be such that com ensation exists between the conductivity 0 metal. I

.As previously stated, the electrical resistance' of metals increases with the temperature, while, on the contrary, the resistance of the oxide decreases with the temperature. The lamp being intended to operate at a predetermined tem erature of the filament, it is essential then t. at for this temperature the increase in resistance of the deposited metal onthe filament should be always reater than the decrease in resistance ofi'ere by the oxids at this temperature.

I claim 1. In a method of making incandescentlamp filaments, the steps consisting in forming a filament of an oxid of .a rare earth metal, and rendering the same conducting by the oxidsand that of the subjecting the same to heat in the presence of a reducing agent and vapors containing a metal of the ruthenium group.

.of ruthenium, and an outer coating of thoriuin oxid.

4. A method of making incandescent-lamp filaments consisting in impregnating a combustible thread with a compound of rare .earth me-tals,-incinerating the thread thus impregnated to produce a filament composed of the oxids of said metals, applying to said 5 filament a metallic compound which is soluble and volatile, reducing-said compound to metal to render the filament conducting and depositing on the filament thus rendered conducting an oxid of a rare earth metal. 1

5. A method of making incandescent-lamp filaments, consistingin impregnating a combustible thread with a compound of rare earth metals, incinerating the thread thus impregna'ted to produce a filament composed of the oxids of said metals, rendering said filament conducting by a plying thereto a metal deposit, passing an e ectric current through said conducting filament to heat the same and while so heated subjecting the filament to a reducing gas and metallic compound and then applying to the filament so treated an oxid o a rare earth metal.

v 6. A method of making incandescent-lamp filaments, conslsting in impregnating a combustible thread with a compound of rareearth metals, incine'rating the thread thus impregnated to produce a filament composed of the oxids of said metals, rendering said fila-' ment conducting by applying thereto a metal deposit, passing an e ectric current through sald conducting filament to heat the same and While so heated subjecting the filament to a reducing-gas and a volatile metallic compound,,and thento the vapors of a thorium compound of acetylacetone.

7. A method of making incandescent-lamp filaments, consisting in impregnating a thread with a rare earth compound, incinerating the same, depositin thereon a refractorymetal, rendering the ament of uniform conductivity by depositing metal thereon where the resistance of the filament is greatest and coating the so-treated filament with anoxid. In testimony whereof I have signed this pecification in the presence of two subscribing witnesses. v

JEAN MICHEL CANELLO. Witnesses:

GASTON DEMOGET, HANSON 0. 00x12. 

